Merge commits with sync-upstream.sh

da0092bc 10f9bd84 297ce820 f34b5cae 920a0e5f 9526874d aa1b889b 20d791ed 3e7b2ea1 21c188b3 8fa41201 515a5dbd c74a7b7e 74c34e72 7006f1b9 ea5e8a9c 793ad901 2e5e4b67 fecf436d 49f608de 49002274 6ad908aa 4f01840b 61ae37c6 486205aa 5d0dbef0 0559fc6e be6944ad a69df3ad b39d431a 0b83b203 09971a3f 9281c9f4 423b6d19 a310e79e 39a36db9 a1102b12

Deal with
  - secp256k1_test_rng removal in commit
    77a19750b4
  - ecmult_gen context simplification after making table static in commit
    3b0c2185ea

include/secp256k1.h

@@ -264,7 +264,7 @@ SECP256K1_API void secp256k1_context_destroy(
  *  undefined.
  *
  *  When this function has not been called (or called with fn==NULL), then the
- *  default handler will be used. The library provides a default handler which
+ *  default handler will be used. The library provides a default handler which
  *  writes the message to stderr and calls abort. This default handler can be
  *  replaced at link time if the preprocessor macro
  *  USE_EXTERNAL_DEFAULT_CALLBACKS is defined, which is the case if the build

include/secp256k1_schnorrsig.h

@@ -111,7 +111,8 @@ typedef struct {
  *  In:    msg32: the 32-byte message being signed.
  *       keypair: pointer to an initialized keypair.
  *    aux_rand32: 32 bytes of fresh randomness. While recommended to provide
- *                this, it is only supplemental to security and can be NULL. See
+ *                this, it is only supplemental to security and can be NULL. A
+ *                NULL argument is treated the same as an all-zero one. See
  *                BIP-340 "Default Signing" for a full explanation of this
  *                argument and for guidance if randomness is expensive.
  */
@@ -120,7 +121,7 @@ SECP256K1_API int secp256k1_schnorrsig_sign(
     unsigned char *sig64,
     const unsigned char *msg32,
     const secp256k1_keypair *keypair,
-    unsigned char *aux_rand32
+    const unsigned char *aux_rand32
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
 
 /** Create a Schnorr signature with a more flexible API.